1. Field of the Invention
The present invention generally relates to power line communication (PLC) systems and methods for data communications over a power distribution system, and more particularly, to a device for facilitating communications through power lines and a method of using the same.
2. Related Art
In general, when a terminal (for example, a computer terminal) performs wired data communication in a home, office or factory environment, a great deal of preparatory engineering work must be performed before a communication system including the terminal is able to begin operations. This is because the communication system needs to install connectors and cables as transmission lines to appropriate positions.
However, with respect to power line communications, the preparatory engineering work in such environments is reduced in comparison with other communication technologies, because almost all of such environments already have in place many commercial power supply lines located in virtually every nook and cranny, while using a commercial power supply, for example, alternating current 100V (50 Hz/60 Hz) in Japan or 120V in the U.S. More particularly, in the case of PLC, it will be possible to establish a data communication line by just connecting a communication apparatus plug to an outlet of the commercial power supply.
JP2000-165304A describes an example of PLC technology utilizing a power line as a data communication line.
In Japan, the frequency band from 2 MHz to 30 MHz is planned to be opened to PLC. At present, many companies are in the process of research and development of PLC technology. However, at this time, there is no PLC standard in Japan, and each company has different specifications for PLC communications relating to protocol, modulating method, and frequency band.
In view of the above, there is high possibility, during actual use, of mixing different PLC communication methods in a same environment. For example, assuming that people who live in an apartment or condominium complex use PLC apparatuses therein, they may use different communication apparatuses made by different manufacturers. In such situation, these different communication apparatuses may be simultaneously connected to a common power line.
In such situation, each communication apparatus may not demodulate signals from the other apparatuses that use different types of PLC communication methods, and may recognize these signals as noise. Because each apparatus may not recognize the existence of the others on the common power line, signals output from different communication apparatuses may collide with each other. Under these conditions, it may become almost impossible to effect a communication. That is, it may become almost impossible for these different PLC apparatuses to coexist on a common power line. In order to facilitate such coexistence, these different apparatuses would need to undergo significant changes to their circuits and controllers.
On the other hand, a plurality of the same kind of PLC apparatuses are able to communicate with each other using a common power line because the signal multiplexing is performed based on time division multiplexing.